(a) Technical Field of the Invention
The present invention relates to a screw bolt, and in particular, to a screw bolt which has specific sloping face to prevent unloading without using a specific tool.
(b) Description of the Prior Art
FIG. 1 shows a conventional screw nut and bolt used for locking. As illustrated, a packing ring 11 is first placed on a working piece 6 and then a bolt 1 is inserted through the packing ring 11 and the working piece to engage with two lock nuts 12 and 13. However, the lock nuts 12 and 13 will become loose if subject to vibration for a long period time. Hence, another method as shown in FIG. 2 is proposed to obviate this drawback. The screw nut 2 is provided with a through hole 21 for an iron wire 22 to pass through. The other end of the wire 22 is mounted onto other work piece. The iron wire prevents the nut 2 from dislocation. However, this conventional structure can be easily unloaded by cutting off the iron wire 22. Therefore, this conventional screw bolt/nut cannot prevent a locked object from burglary.
Accordingly, it is an aspect of the present invention to provide an improved structure of an anti-burglar screw bolt having a pad and a nut, the bolt including a bolt head and a bolt shaft, characterized in that the bolt head is hexagonal with the inner edges being arranged with equal angle and provided with sloping faces continuing from one to another such that the shallowest region of a fore notch of the sloping face is the deepest region of a subsequent notch of the sloping face, and connection region of each of the sloping face being a blocking face having a high-low depression; the pad is flat and circular having a diameter equivalent to the largest diameter of the bolt head, the center of the pad is provided with a through hole having a hole diameter larger than that of the bolt shaft, one face of the pad is formed into a continuing sloping face corresponding to the sloping face of the individual bolt head such that the thinnest region of the fore sloping face is the thickest region of the subsequent sloping face and the individual connecting region is formed into a holding face having a high-low depression, and the other face of the pad is provided with a plurality of equally arranged sharp engaging straps, each of the strap has an upright face and a sloping face and the sloping direction of the sloping face is similar to that of the continuing sloping face of the pad; and the nut is hexagonal and the inner edge of each side thereof is provided with a sloping face corresponding to the continuing sloping face, the connection region of each sloping face is also formed into a blocking face having a high-low depression.
The foregoing object and summary provide only a brief introduction to the present invention. To fully appreciate these and other objects of the present invention as well as the invention itself, all of which will become apparent to those skilled in the art, the following detailed description of the invention and the claims should be read in conjunction with the accompanying drawings. Throughout the specification and drawings identical reference numerals refer to identical or similar parts.
Many other advantages and features of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.